Conventionally, a semiconductor manufacturing apparatus performs processing such as dry etching (for example, plasma etching) on a semiconductor wafer (for example, silicon wafer). In order to enhance accuracy of the dry etching, the semiconductor wafer needs to be reliably fixed. As fixing means for fixing a semiconductor wafer, an electrostatic chuck which fixes a semiconductor wafer by means of an electrostatic attraction force has been proposed (refer to Patent Document 1, for example).
Specifically, an electrostatic chuck described in Patent Document 1 has an attraction electrode in a ceramic insulating plate, and causes a semiconductor wafer to be attracted to an upper surface (attraction surface) of the ceramic insulating plate by using an electrostatic attraction force generated when a voltage is applied to the attraction electrode. This electrostatic chuck is formed by joining a metal base to a lower surface (joint surface) of the ceramic insulating plate.
In recent years, a technique has been known in which an electrostatic chuck is provided with a function of controlling (heating or cooling) the temperature of a semiconductor wafer in order to suitably perform processing on the semiconductor wafer attracted to an attraction surface.
For example, a technique has been known in which a heater electrode (formed in a spiral shape) is provided as a heating element in a ceramic insulating plate, and the ceramic insulating plate is heated by the heater electrode to heat a semiconductor wafer on an attraction surface.
Furthermore, Patent Document 1 discloses a technique in which a cooling gas flow path that opens at an attraction surface is provided in the ceramic insulating plate, and a cooling gas (e.g., helium gas) that flows in the cooling gas flow path is brought into contact with the semiconductor wafer on the attraction surface to cool the semiconductor wafer.
Besides, in the electrostatic chuck having the above-mentioned structure, since the ceramic insulating plate and the metal base have difference thermal expansion coefficients, when the temperature changes, warpage may occur in the electrostatic chuck due to a thermal stress generated between the ceramic insulating plate and the metal base.
As a countermeasure against such warpage, a technique has been proposed in which a stress reducing layer is provided between the ceramic insulating plate and the metal base (refer to Patent Document 2, for example).